Conventional web converting equipment uses some sort of transport mechanism for moving the web at high rates of speeds through a series of processing stations. Typically such processing stations includes corrosive environments through which the web must be transported. For instance, in existing photographic film processors used to develop and fix photosensitive elements which are subjected to x-ray, visible and other radiation, the web is transported via a series of rollers defining a web transport path through a sequence of processing stations including wash and dry stations.
Very often during processing, photosensitive media are coated with a magnetic layer to enable it to gather digital information. The magnetic layer often contains a small fraction of hard inorganic particles to facilitate cleaning of the magnetic head which are used for reading digital information in a read-out device. Photographic films are also coated with an "anti-stat" layer for dissipating static charges from the moving web. The anti-stat layers generally contain hard abrasive particles like tin oxide, antimony oxide, vanadium oxide and the like.
Moreover, process and transport apparatus for photosensitive web or other media is another well known applications requiring a web transport mechanism. Such equipment may include automatic processing of the media for thermal, ink jet or silver halide-based photographic printing, and the like. The apparatus automatically transports sheets or webs or strips of photosensitive films, photosensitive papers or specially coated papers or plain papers. For photosensitive elements, this apparatus transports from a feed end of a film transport path, through a sequence of chemical processing tanks in which the media is developed, fixed, and washed, and then through a dryer to a discharge or receiving end. The processing equipment typically has a fixed film (media) path length, so final image quality depends on factors including transport speed which determines length of time the media is in solution, and the temperature and composition of the processing chemicals.
In general, many elements of devices (such as, photographic film processors and thermal and ink jet printers) exposed to harsh chemicals are made from AISI 300 series stainless steel or engineering plastic for reasons of mechanical strength, lower cost, and relatively good corrosion resistance. Engineering plastics are typically used as bushings and gears because of their relatively low coefficient of friction against stainless steel. Furthermore, photographic transport apparatus exposed in normal ambient conditions are also prone to wear and corrosion because of the abrasive and corrosive nature (depending on their relative humidity) of the photographic elements. Although stainless steel shafts have considerable strength and corrosion resistance, they are prone to wear with time and are also susceptible to corrosion when they come in contact with harsh chemicals which are used in "fixer" solution for developing photographic films. To overcome these drawbacks, many engineering plastics are reinforced with glass and carbon fibers or other hard inorganic particles to improve the strength and wear resistance at the expense of proneness to corrosion. Another problem associated with plastic components operating in a fluid environment is that they tend to swell and become dimensionally unstable.
Therefore, a need persists for an apparatus having a polymeric/inorganic composite media bearing surface for conveying abrasive web such as, photographic media.